For example, in wireless communication network using internet protocol (IP) groups (which network will occasionally be referred to as “radio IP network” hereinafter), as disclosed in e.g. C. Perkins, “IP Mobility Support (RFC2002)”, [online], October 1996, IETF, [searched on 15 Mar. 2006], internet<URL: http://www.ietforg/rfc/rfc2002.txt, what is called “mobile IP” is prescribed to improve mobility of wireless communication apparatuses.
In mobile IP, Care of Address, which is dynamically allocated in accordance with positions of a wireless communication apparatus, is used.